- 12 - 
From thp experiments it is concluded that derris furnishes a very 
efficient insecticide, particularly when used as a powder, against 
ectoparasites. It is effective, easily applied, not repugnant to the 
animal or man, and retains its insecticidal properties unaltered in the 
open air. It should "be used about the same as pyrethrum powder, and in 
the 20 percent derris-80 percent tobacco dust mixture has a killing power 
about as effective as that of commercial pyrethrum. Its stability in 
insecticidal power makes it superior to pyrethrum even at a slightly higher 
price. It seems, however, to lack the instantaneous effect of pyrethrum and is 
not effective against flies when blown into the air. As a check against 
roaches, ants, and insect ectoparasites, it is fully the equal of pyrethrum 
as ordinarily purchased. 
The 20 percent derris-80 percent tobacco dust mixture was effective 
but slow in action against roaches. Roaches forced to run through the 
powder and then confined in cages or small glass jars all died with 24 
hours. These roaches were forced to run over a considerable depth of the 
powder and were thoroughly coated with it. The powder was also mixed with 
flour and a little sugar, and roaches were allowed to feed upon it. It 
proved an effective stomach poison, killing all the roaches experimented 
upon. 
Howard (99) in 1922 called attention to the work of Bishopp and 
associates, who found derris to be very effective for use in the dust 
form against lice of cattle and other domestic animals as well as against 
fleas* 
Jack and Sands (53) in 1922 reported that spraying with tuba/ mix- 
tures is one of the means recommended for controlling the cotton stainer. 
1923 
Lewin (57) in 1923 wrote that in Sumatra the diluted root sap of 
PQ^^^s elliptica is used to kill caterpillars on young tobacco plants, but 
too great a quantity kills the tobacco. 
Hadwen (48) in 1923 referred to the method of killing Hypo derm a 
larvae by the application to the warble holes of ointments containing 
iodoform or derris. 
Jack (52) in 1923 wrote that the juice extracted from Derris 
elliptica is most effective in combating the stem-boring insects attack- 
ing rice, Schoenobius bipunctif erus and Diatraea auricilia , but can be 
used only where the padi is grown in water which is not mixed later 
with the drinking supply. 
According to Gimlette (45), writing in 1923, H. E. Durham in 1902 
commenced a series of experiments with tuba as a larvicide in the Federated 
Malay States. Dr. Durham found that the most sensitive animals are perhaps 
the daphnid Crustacea. Tadpoles and water-snails are also easily killed. 
Caterpillars are easily poisoned; specially sensitive is the gooseberry 
